1 /* GSSAPI/krb5 support for FTP - loosely based on old krb4.c
2  *
3  * Copyright (c) 1995, 1996, 1997, 1998, 1999 Kungliga Tekniska H�gskolan
4  * (Royal Institute of Technology, Stockholm, Sweden).
5  * Copyright (c) 2004 - 2017 Daniel Stenberg
6  * All rights reserved.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  *
12  * 1. Redistributions of source code must retain the above copyright
13  *    notice, this list of conditions and the following disclaimer.
14  *
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  *
19  * 3. Neither the name of the Institute nor the names of its contributors
20  *    may be used to endorse or promote products derived from this software
21  *    without specific prior written permission.
22  *
23  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33  * SUCH DAMAGE.  */
34 
35 #include "curl_setup.h"
36 
37 #if defined(HAVE_GSSAPI) && !defined(CURL_DISABLE_FTP)
38 
39 #ifdef HAVE_NETDB_H
40 #include <netdb.h>
41 #endif
42 
43 #include "urldata.h"
44 #include "curl_base64.h"
45 #include "ftp.h"
46 #include "curl_gssapi.h"
47 #include "sendf.h"
48 #include "curl_sec.h"
49 #include "warnless.h"
50 
51 /* The last 3 #include files should be in this order */
52 #include "curl_printf.h"
53 #include "curl_memory.h"
54 #include "memdebug.h"
55 
56 static int
krb5_init(void * app_data)57 krb5_init(void *app_data)
58 {
59   gss_ctx_id_t *context = app_data;
60   /* Make sure our context is initialized for krb5_end. */
61   *context = GSS_C_NO_CONTEXT;
62   return 0;
63 }
64 
65 static int
krb5_check_prot(void * app_data,int level)66 krb5_check_prot(void *app_data, int level)
67 {
68   (void)app_data; /* unused */
69   if(level == PROT_CONFIDENTIAL)
70     return -1;
71   return 0;
72 }
73 
74 static int
krb5_decode(void * app_data,void * buf,int len,int level UNUSED_PARAM,struct connectdata * conn UNUSED_PARAM)75 krb5_decode(void *app_data, void *buf, int len,
76             int level UNUSED_PARAM,
77             struct connectdata *conn UNUSED_PARAM)
78 {
79   gss_ctx_id_t *context = app_data;
80   OM_uint32 maj, min;
81   gss_buffer_desc enc, dec;
82 
83   (void)level;
84   (void)conn;
85 
86   enc.value = buf;
87   enc.length = len;
88   maj = gss_unwrap(&min, *context, &enc, &dec, NULL, NULL);
89   if(maj != GSS_S_COMPLETE) {
90     if(len >= 4)
91       strcpy(buf, "599 ");
92     return -1;
93   }
94 
95   memcpy(buf, dec.value, dec.length);
96   len = curlx_uztosi(dec.length);
97   gss_release_buffer(&min, &dec);
98 
99   return len;
100 }
101 
102 static int
krb5_overhead(void * app_data,int level,int len)103 krb5_overhead(void *app_data, int level, int len)
104 {
105   /* no arguments are used */
106   (void)app_data;
107   (void)level;
108   (void)len;
109   return 0;
110 }
111 
112 static int
krb5_encode(void * app_data,const void * from,int length,int level,void ** to)113 krb5_encode(void *app_data, const void *from, int length, int level, void **to)
114 {
115   gss_ctx_id_t *context = app_data;
116   gss_buffer_desc dec, enc;
117   OM_uint32 maj, min;
118   int state;
119   int len;
120 
121   /* NOTE that the cast is safe, neither of the krb5, gnu gss and heimdal
122    * libraries modify the input buffer in gss_wrap()
123    */
124   dec.value = (void *)from;
125   dec.length = length;
126   maj = gss_wrap(&min, *context,
127                  level == PROT_PRIVATE,
128                  GSS_C_QOP_DEFAULT,
129                  &dec, &state, &enc);
130 
131   if(maj != GSS_S_COMPLETE)
132     return -1;
133 
134   /* malloc a new buffer, in case gss_release_buffer doesn't work as
135      expected */
136   *to = malloc(enc.length);
137   if(!*to)
138     return -1;
139   memcpy(*to, enc.value, enc.length);
140   len = curlx_uztosi(enc.length);
141   gss_release_buffer(&min, &enc);
142   return len;
143 }
144 
145 static int
krb5_auth(void * app_data,struct connectdata * conn)146 krb5_auth(void *app_data, struct connectdata *conn)
147 {
148   int ret = AUTH_OK;
149   char *p;
150   const char *host = conn->host.name;
151   ssize_t nread;
152   curl_socklen_t l = sizeof(conn->local_addr);
153   struct Curl_easy *data = conn->data;
154   CURLcode result;
155   const char *service = data->set.str[STRING_SERVICE_NAME] ?
156                         data->set.str[STRING_SERVICE_NAME] :
157                         "ftp";
158   const char *srv_host = "host";
159   gss_buffer_desc input_buffer, output_buffer, _gssresp, *gssresp;
160   OM_uint32 maj, min;
161   gss_name_t gssname;
162   gss_ctx_id_t *context = app_data;
163   struct gss_channel_bindings_struct chan;
164   size_t base64_sz = 0;
165   struct sockaddr_in **remote_addr =
166     (struct sockaddr_in **)&conn->ip_addr->ai_addr;
167   char *stringp;
168 
169   if(getsockname(conn->sock[FIRSTSOCKET],
170                  (struct sockaddr *)&conn->local_addr, &l) < 0)
171     perror("getsockname()");
172 
173   chan.initiator_addrtype = GSS_C_AF_INET;
174   chan.initiator_address.length = l - 4;
175   chan.initiator_address.value = &conn->local_addr.sin_addr.s_addr;
176   chan.acceptor_addrtype = GSS_C_AF_INET;
177   chan.acceptor_address.length = l - 4;
178   chan.acceptor_address.value = &(*remote_addr)->sin_addr.s_addr;
179   chan.application_data.length = 0;
180   chan.application_data.value = NULL;
181 
182   /* this loop will execute twice (once for service, once for host) */
183   for(;;) {
184     /* this really shouldn't be repeated here, but can't help it */
185     if(service == srv_host) {
186       result = Curl_ftpsend(conn, "AUTH GSSAPI");
187       if(result)
188         return -2;
189 
190       if(Curl_GetFTPResponse(&nread, conn, NULL))
191         return -1;
192 
193       if(data->state.buffer[0] != '3')
194         return -1;
195     }
196 
197     stringp = aprintf("%s@%s", service, host);
198     if(!stringp)
199       return -2;
200 
201     input_buffer.value = stringp;
202     input_buffer.length = strlen(stringp);
203     maj = gss_import_name(&min, &input_buffer, GSS_C_NT_HOSTBASED_SERVICE,
204                           &gssname);
205     free(stringp);
206     if(maj != GSS_S_COMPLETE) {
207       gss_release_name(&min, &gssname);
208       if(service == srv_host) {
209         failf(data, "Error importing service name %s@%s", service, host);
210         return AUTH_ERROR;
211       }
212       service = srv_host;
213       continue;
214     }
215     /* We pass NULL as |output_name_type| to avoid a leak. */
216     gss_display_name(&min, gssname, &output_buffer, NULL);
217     Curl_infof(data, "Trying against %s\n", output_buffer.value);
218     gssresp = GSS_C_NO_BUFFER;
219     *context = GSS_C_NO_CONTEXT;
220 
221     do {
222       /* Release the buffer at each iteration to avoid leaking: the first time
223          we are releasing the memory from gss_display_name. The last item is
224          taken care by a final gss_release_buffer. */
225       gss_release_buffer(&min, &output_buffer);
226       ret = AUTH_OK;
227       maj = Curl_gss_init_sec_context(data,
228                                       &min,
229                                       context,
230                                       gssname,
231                                       &Curl_krb5_mech_oid,
232                                       &chan,
233                                       gssresp,
234                                       &output_buffer,
235                                       TRUE,
236                                       NULL);
237 
238       if(gssresp) {
239         free(_gssresp.value);
240         gssresp = NULL;
241       }
242 
243       if(GSS_ERROR(maj)) {
244         Curl_infof(data, "Error creating security context\n");
245         ret = AUTH_ERROR;
246         break;
247       }
248 
249       if(output_buffer.length != 0) {
250         char *cmd;
251 
252         result = Curl_base64_encode(data, (char *)output_buffer.value,
253                                     output_buffer.length, &p, &base64_sz);
254         if(result) {
255           Curl_infof(data, "base64-encoding: %s\n",
256                      curl_easy_strerror(result));
257           ret = AUTH_ERROR;
258           break;
259         }
260 
261         cmd = aprintf("ADAT %s", p);
262         if(cmd)
263           result = Curl_ftpsend(conn, cmd);
264         else
265           result = CURLE_OUT_OF_MEMORY;
266 
267         free(p);
268         free(cmd);
269 
270         if(result) {
271           ret = -2;
272           break;
273         }
274 
275         if(Curl_GetFTPResponse(&nread, conn, NULL)) {
276           ret = -1;
277           break;
278         }
279 
280         if(data->state.buffer[0] != '2' && data->state.buffer[0] != '3') {
281           Curl_infof(data, "Server didn't accept auth data\n");
282           ret = AUTH_ERROR;
283           break;
284         }
285 
286         _gssresp.value = NULL; /* make sure it is initialized */
287         p = data->state.buffer + 4;
288         p = strstr(p, "ADAT=");
289         if(p) {
290           result = Curl_base64_decode(p + 5,
291                                       (unsigned char **)&_gssresp.value,
292                                       &_gssresp.length);
293           if(result) {
294             failf(data, "base64-decoding: %s", curl_easy_strerror(result));
295             ret = AUTH_CONTINUE;
296             break;
297           }
298         }
299 
300         gssresp = &_gssresp;
301       }
302     } while(maj == GSS_S_CONTINUE_NEEDED);
303 
304     gss_release_name(&min, &gssname);
305     gss_release_buffer(&min, &output_buffer);
306 
307     if(gssresp)
308       free(_gssresp.value);
309 
310     if(ret == AUTH_OK || service == srv_host)
311       return ret;
312 
313     service = srv_host;
314   }
315   return ret;
316 }
317 
krb5_end(void * app_data)318 static void krb5_end(void *app_data)
319 {
320     OM_uint32 min;
321     gss_ctx_id_t *context = app_data;
322     if(*context != GSS_C_NO_CONTEXT) {
323 #ifdef DEBUGBUILD
324       OM_uint32 maj =
325 #endif
326       gss_delete_sec_context(&min, context, GSS_C_NO_BUFFER);
327       DEBUGASSERT(maj == GSS_S_COMPLETE);
328     }
329 }
330 
331 struct Curl_sec_client_mech Curl_krb5_client_mech = {
332     "GSSAPI",
333     sizeof(gss_ctx_id_t),
334     krb5_init,
335     krb5_auth,
336     krb5_end,
337     krb5_check_prot,
338     krb5_overhead,
339     krb5_encode,
340     krb5_decode
341 };
342 
343 #endif /* HAVE_GSSAPI && !CURL_DISABLE_FTP */
344